When a problem affects a whole industry, industry wide standards are implemented to address that issue. When a new problem impacts an existing standard, that standard is updated to present a solution to the new problem. We are familiar with these standards bodies, ISO, ASTM, SAE, ASE, NFPA, STI, PEI, etc.
SAE J1488 is the industry standard “To determine the ability of a fuel/water separator to separate emulsified or finely dispersed water from fuels.” This standard is revised as required; the latest revision of this standard is SAE J1488_201010.
Why the Revision?
Water is a fact of life in diesel and diesel storage. Water in the fuel can cause a host of problems, from damage to the diesel engines to enhancing microbial growth which can clog filters and shut down gensets. In pre ULSD diesel, practically 100% of water was efficiently removed by filters, either absorbent or coalescing, and by implementing good tank housekeeping procedures, such as draining the water from the bottom of the tanks as required.
ULSD (Ultra Low Sulfur Diesel) was introduced to combat the huge environmental impact of adding sulfur to the atmosphere, notably the severe impact of acid rain on rivers and lakes and forests, not to mention the health issues affecting humans over time. The process of removing the sulfur from diesel changed the chemistry of the fuel. First to be noticed was the reduction of the natural lubricity normally found in pre ULSD diesel; there was much more wear and tear on diesel engines. This problem was addressed by adding lubricity back into the fuel with additives. What was not noticed initially was that the water in the fuel was much more tightly held to the ULSD than before. Traditional filters lost a great deal of efficiency in removing water from diesel. (Uptime Report, Biodiesel). In addition, the additives added to bring lubricity back to the fuel reduced the interfacial tension between diesel and water. This meant that the water could more easily mix with the diesel. Less of the water in storage tanks was free standing on the bottom, and more was absorbed into the fuel itself. With biodiesel fuels the interfacial tension is much lower, and volumes of emulsified water absorbed are dramatically higher.
Microbial growth in pre ULSD diesel was limited along the water/diesel interface, where there is diesel for food and water for life. Most of the emulsified water in the volume of the pre ULSD fuel precipitated out to become free standing water on the bottom. Biodiesel blends absorb much more water, and the emulsified water is so tightly held that it remains emulsified throughout the volume of the diesel. Microbes now have a much greater volume to grow in, such that there is an explosion of microbial growth in biodiesel blends. A small percentage of the microbes produce acid; in pre ULSD fuel it was such a small amount the acidic levels were rarely noticed. Todays biodiesel fuels have so much more microbial growth the acid levels are reaching a state that within a year or so that corrosion is now seen in the diesel infrastructure, affecting storage tanks, piping, and diesel engines such as emergency generators.
SAE updated their standard to SAE J1488_201010 to address the great increase in the amount of emulsified water absorbed in ULSD and biodiesel blends. SAE tested the efficiency of filters to remove the tightly bound emulsified water from these fuels. The removal/control of the emulsified water also controls the microbial growth, such that acidification is no longer an issue in these treated fuels.
The test procedure entails injecting up to 2500 ppm emulsified water into diesel with an interfacial tension of 15 mN/m, similar to biodiesel blends available today, and then filtering the fuel to provide an efficiency rating of the filters capability of removing the emulsified water. Since OEM manufacturers of gensets have warranty based on 200 ppm water or less, filters need at least an efficiency rating of 92% or better to protect the infrastructure.
SAE J1488_201010 is the industry standard to protect biodiesel infrastructures; it should be a mandatory requirement for installation of all fuel/water separators and diesel filters.
Industry Reference Documents
For further reading on biodiesel, water and corrosion, read the following. All the references below have the same common recommendation – dry the fuel.
“Corrosion in Systems for Storage and Transportation of Petroleum Products and Biofuels: Identification, Monitoring and Solutions”, Publisher: Springer Science & Business Media, Feb 17, 2014, ISBN: 9789400778849
Degradation of Fiberglass Underground Storage Tanks May 04, 2015
Battelle Report – “Corrosion in Systems Storing and Dispensing Ultra Low Sulfur Diesel (ULSD), Hypotheses Investigation”
STI Steel Tank Institute “Keeping Water Out of Your Storage System”
PEI Petroleum Equipment Institute (PEI) Recommended Practice (RP) 2014 Final Draft RP 1400 “Recommended Practices for the Design and Installation of Fuelling Systems for Emergency Generators, Stationary Diesel Engines and Oil Burner Systems”
SAE Emulsified Water/Fuel Separation Test Procedure